Bacillaria is a colony in which numerous individual diatoms are connected. The individual diatoms are lined up side by side, which looks like a window blind when the colony is contracted. When the colony stretches out, the diatoms are connected nearly end to end in a long chain-like structure. Bacillaria usually moves in a straight line when extended, but can change directions freely when contracted. Various small diatoms, aggregates and crystals are stuck to Bacillaria and move along with it.